Whole cell patch clamp technology provides a means for measuring membrane-capacitance of cell channels. Applications included measuring membrane capacity due to the action of synexin on medullary chromaffin cells. Programmed pipette potential changes were obtained from a D/A converter of a PACE minicomputer system. Current transients were obtained and read into the high speed (500 kHz) A/D converter of this system. A moderate speed (150 kHz) PC-based microcomputer system is currently being developed for membrane capacitance measurements.